The present invention relates to a semiconductor system. A conventional semiconductor system includes a planar anode contact and a planar cathode contact and a first volume of n-conductive semiconductor material, which extends between the planar anode contact and the planar cathode contact. A direction pointing from the anode contact to the cathode contact defines a depth direction. The semiconductor system has at least one p-conductive area having an anode-side end and a cathode-side end and which extends from the anode-side end in the depth direction toward the cathode-side end without reaching the cathode-side end.
When alternating current or three-phase current is rectified, alternating current bridges (rectifiers) are used. Semiconductor diodes having a PN junction of silicon are mostly used as rectifying elements. In high-power systems, power semiconductor diodes, which are suitable for current densities of more than 500 A/cm2 and high operating temperatures at depletion layer temperatures of Tj˜225° C., are used. Typically, voltage drop UF is approximately 1 volt in the direction of flow (i.e., the forward voltage) at the high currents used. In systems which are designed for relatively low system voltages, which is the case, for example, in motor vehicle generator diodes, the maximum cutoff voltage of the diodes may be additionally limited. These diodes may be operated at high currents in cutoff voltage breakdown, at least for short times. This may be used to limit the system voltage or vehicle electrical system voltage. Frequently, a voltage limitation in the range of 20-50 volts is needed.
The forward voltage of PN diodes results in conducting-state power losses and thus in an efficiency degradation of the system, for example, a generator. The conducting-state power losses result in undesirable heating of the components, which must be counteracted by complex measures for dissipating heat from the rectifier to the surroundings using heat sinks and/or fans.
For reducing the conducting-state power losses, other components such as improved Schottky diodes, pseudo-Schottky rectifiers, etc., or actively controlled power transistors are increasingly provided. German Patent Application No. DE 10 2004 056 663 A1 describes in this connection a trench MOS barrier Schottky diode including an integrated PN diode.
The existing approaches are either relatively complex, as in the case of actively controlled power transistors, and/or they are difficult to integrate into a single housing, for example, into a press-fit diode housing for motor vehicle generators, or they have only a limited effect. Thus, in the case of pure diode approaches, it has hitherto not been possible to overcome the correlation between forward voltage and the cutoff currents. The smaller the forward voltage, the higher the cutoff currents.